Users: When deleting users, exclude the current user from the content…

… existence check.
The current user cannot be deleted, so the check is redundant in that context and should only be done for other users.
Props mt8.biz, SergeyBiryukov.
Fixes #47851.
git-svn-id: https://develop.svn.wordpress.org/trunk@45806 602fd350-edb4-49c9-b593-d223f7449a82